Replacing "Mission Begins" Sounds

Lamech

L1: Registered
May 21, 2009
18
8
Its the voice overs done by the announcer during setup time.

What I am wanting to do is replace these sounds with custom ones. That is all, I know its possible just unsure how.

I've done my best in search, but could not find anything pertaining to this. Forgive me if it has, you can redirect me there if so :D